1. Field of the Invention
This invention relates to a device for supporting various kinds of rollers for conveying a sheet material, to a sheet-material feeding device in which such a roller supporting device is used as a separation rotating member of a separation conveying unit, to an original-reading device in which such a sheet-material feeding device is applied to a unit for feeding a sheet-like original, and to an image recording apparatus, such as a copier, a printer or the like, in which such a sheet-material feeding device is applied to a unit for feeding a sheet material for recording.
2. Description of the Related Art
An automatic original-feeding device, serving as an example of the above-described sheet-material feeding device, used in an original-reading apparatus is configured as shown in FIGS. 13(a) and 13(b). That is, the automatic original-feeding device includes a pickup roller 102 for feeding a plurality of sheet-like originals 101 mounted on a sheet-material mounting unit 100, and a separation conveying unit 104 for individually separating the unseparated originals 101 fed by the pickup roller 102 and conveying each of the separated originals to a reading unit 103 provided downstream of pickup roller 102.
The separation conveying unit 104 is a so-called retard roller separation system (or method), and comprises a feed roller 105 for conveying the original 101 toward the downstream side in the feeding direction, and a retard roller 106, serving as reverse-rotation separation means, rotatably driven in a direction opposite to the feeding direction of the original 101 and in pressure contact with the feed roller 105 with a predetermined pressure.
The retard roller 106 is rotatably supported on a pair of supporting levers 109, 109 swingably mounted on a supporting shaft 108 provided between a pair of protruded pieces 107a, 107a of a bracket 107.
A roller shaft 110 is threaded through the retard roller 106, and the retard roller 106 is integrally fixed on the roller shaft 110 by parallel pins (not shown). Both ends of the roller shaft 110 are rotatably supported on swinging ends of the pair of supporting levers 109, 109.
The supporting lever 109 has an L-like shape, and the bending portion of the supporting lever 109 is pivoted on the supporting shaft 108. The retard roller 106 is rotatably supported on one swinging end of the supporting lever 109, and a connection shaft 111 is inserted between the other swinging ends of the supporting levers 109, 109. A pressing lever 112 for pressing the supporting levers 109 via the connection shaft 111 to make the retard roller 106 in pressure contact with the feed roller 105 is provided on the supporting shaft 108. The pressing lever 112 is urged in a predetermined direction by a spring member 115.
The movement of the roller shaft 110, the supporting shaft 108 and the connection shaft 111 in the axial direction is regulated by stop rings 160, each comprising an E-ring or the like.
In the above-described conventional structure, the feed roller 105 is exposed and can be exchanged when an upper opening/closing guide is opened. However, the retard roller 106 is exchanged in a different manner. That is, first, as shown in FIG. 14, a white guide member 114 incorporated within a main body 161 of the device screwed at four points is exposed. The white guide member 114 serves as the background of the reading unit 103. Then, the white guide member 114 screwed at two points is separated from the main body 161 of the device to expose a bracket 107 incorporated inside the main body 161 of the device, and the bracket 107 is separated by removing screws at the two points. In order to take out the retard roller 106 from the bracket 107, it is necessary to separate the five stop rings 160, the spring member 115, the roller shaft 110, the supporting shaft 108, the connection shaft 111, the supporting levers 109 and the pressing lever 112.
Accordingly, it is almost impossible for the user to exchange the retard roller 106, and a serviceman for performing maintenance is required. Since it is almost impossible for the user to exchange the retard roller 106, the life of the entire device for typical maintenance free products is determined by the life of the retard roller 106.
In order to solve such a problem, an approach as shown in FIG. 15 can be considered. That is, the roller shaft for suppporting the retard roller 106, serving as the main body of the roller, is divided into right and left supporting shafts 121 and 122, and the one supporting shaft 121 is made to be slidable in the thrust direction. The movable supporting shaft 121 is urged by a spring member 123 toward the retard roller 106 to support it, and an opening 125 capable of receiving the retard rollers 106 is provided in a guide member 124. Thus, the retard roller 106 can be detached by moving the movable supporting shaft 121 against the urging force of the spring member 123 through the opening 125 provided in the guide member 124, without disassembling the device as in the conventional structure.
In this case, however, since the movable supporting shaft 121 is supported only by the urging force of the spring member 123, the retard roller 106 may detach due to vibration or the like. Furthermore, since the supporting shaft 121 is always urged in the thrust direction, an unnecessary load torque may be produced in the retard roller 106.